A flexible modified microcapsule-coated anhydride curing agent, its preparation method, and the resulting film.

Abstract

This invention provides a flexible modified microcapsule-coated anhydride curing agent, its preparation method, and the resulting film. Urea, formaldehyde, and the flexible modified monomer n-butylamine are reacted with an alkaline catalyst to generate a flexible urea-formaldehyde resin prepolymer. This prepolymer is then mixed and emulsified with the anhydride curing agent and an accelerator to form a flexible microcapsule-coated anhydride curing agent. The presence of flexible carbon chains in the capsule wall material effectively mitigates cracking caused by the large shrinkage during microcapsule curing, improving the uniformity and density of the capsule wall. Furthermore, the curing agent is less prone to cracking during transportation, high-speed stirring, and coating.

Description

Technical Field

[0001] This invention relates to the field of epoxy resin adhesive technology, specifically to a flexible modified microcapsule-coated anhydride curing agent, its preparation method, and the adhesive film thereof. Background Technology

[0002] Epoxy resin possesses excellent physical and mechanical properties, electrical insulation properties, heat resistance, and adhesive properties, making it widely used in the semiconductor industry. With the increasing integration and thinning of semiconductor technology, the requirements for epoxy resin adhesives used as semiconductor packaging materials are also becoming more stringent. Semiconductor packaging materials are composed of epoxy resin, curing agents, and other additives, with epoxy resin being one of the key raw materials determining the quality of the packaging material. However, as a general-purpose epoxy resin material, its high crosslinking density and internal stress, along with the large number of hydroxyl groups in the crosslinked network structure, result in poor stability. This makes it unable to meet the specific application requirements of epoxy resin crosslinking agents in recent years' semiconductor development, such as storage stability.

[0003] Currently, while multi-component epoxy resin adhesives exhibit good stability, they suffer from storage difficulties. During the preparation of multi-component adhesives, measurement errors and uneven mixing are easily introduced, subsequently affecting the adhesive's performance. Furthermore, when using conventional latent curing agents, materials with excellent storage stability often have low curing rates, requiring high temperatures or long curing times. On the other hand, while adding accelerators can lower the curing temperature or time, this correspondingly reduces storage stability. Clearly, storage stability and adhesive performance are often incompatible.

[0004] In the existing technology, microencapsulated curing agents can solve the above problems well. However, the microencapsulated curing agents currently on the market have problems such as high-speed stirring, microcapsule rupture during transportation after mixing with glue, resulting in premature gelation of the glue, and microcapsule rupture during coating, resulting in air bubble perforation. Therefore, there is an urgent need for a highly active epoxy microencapsulated curing agent that is easy to store and use. Summary of the Invention

[0005] In view of this, the purpose of this application is to provide a flexible modified microcapsule-coated anhydride curing agent, its preparation method and film, which effectively improves the cracking problem caused by the large shrinkage of microcapsule curing by adding flexible carbon chains to the capsule wall material of the curing agent, improves the uniformity and density of the capsule wall, and is not easy to break during transportation, high-speed stirring and coating.

[0006] To achieve the above objectives, this application provides the following technical solution:

[0007] A method for preparing a flexible modified microcapsule-coated anhydride curing agent includes the following steps:

[0008] S1. Preparation of flexible urea-formaldehyde resin prepolymer: A flexible urea-formaldehyde resin prepolymer is prepared by mixing formaldehyde, urea and a flexible modifier;

[0009] S2. Preparation of emulsion: Emulsifier, resorcinol, curing agent and accelerator are added to an aqueous emulsifier solution to form a stable oil-in-water (O / W) type emulsion;

[0010] S3. Preparation of curing agent

[0011] The flexible urea-formaldehyde resin prepolymer prepared in S1 and the emulsion prepared in S2 are mixed and then cured to obtain an emulsion-like flexible microcapsule curing agent.

[0012] S4. Surface Treatment

[0013] A surface modifier is added to the flexible microcapsule curing agent prepared in S3 for reaction. The surface modifier is then grafted onto the flexible microcapsule curing agent for surface treatment to obtain a flexible urea-formaldehyde resin microcapsule curing agent with epoxy functional groups grafted onto its surface.

[0014] Preferably, in S1, the flexible modifier is a straight-chain alkylamine with the structural formula CH3(CH2). n NH2, n = 3 to 5.

[0015] Preferably, in S1, the flexible modifier is n-butylamine.

[0016] Preferably, the curing agent is an acid anhydride curing agent; the accelerator is 2-ethyl-4-methylimidazole.

[0017] Preferably, the anhydride curing agent is any one of methyltetrahydrophthalic anhydride, maleic anhydride, and hexahydrophthalic anhydride.

[0018] Preferably, the surface modifier is an alkoxy compound containing -Si-O- bonds.

[0019] Preferably, the surface modifier is KH560.

[0020] Preferably, the mass ratio of the flexible modifier to formaldehyde is 1:4 to 8.

[0021] Preferably, the mass ratio of the surface modifier to formaldehyde is 0.02 to 0.1:1.

[0022] The flexible modified microcapsule-coated anhydride curing agent prepared using the above technical solution incorporates linear alkylamines as flexible carbon chain groups into urea-formaldehyde resin, which can improve the flexibility of urea-formaldehyde resin and avoid the problem of microcapsule structure cracking caused by microcapsule curing shrinkage.

[0023] The microcapsules in this invention are flexible urea-formaldehyde resin microcapsules synthesized from urea, formaldehyde, and flexible modified monomers. These microcapsules are then mixed and emulsified with anhydride curing agents and their accelerators to form a latent curing agent for epoxy microcapsules. The surface of the microcapsule curing agent is then modified with KH560, resulting in epoxy groups on the microcapsule surface. The flexible urea-formaldehyde resin in the microcapsule curing agent exhibits increased flexibility due to the presence of flexible carbon chains, effectively mitigating cracking problems caused by the large shrinkage of the microcapsules during curing. This improves the uniformity and density of the capsule wall and prevents premature gelation caused by microcapsule rupture during transportation or high-speed stirring, as well as air bubble perforation during coating. Rapid stirring is possible without concern about microcapsule rupture, saving raw materials, time, and labor costs. The epoxy groups on the microcapsule surface ensure more uniform dispersion in the epoxy resin, reducing sedimentation and resulting in excellent curing efficiency and uniformity. Furthermore, this invention aims to provide a solid film using the curing agent of this invention.

[0024] Taking n-Butylamine as an example, its reaction mechanism is as follows:

[0025] The chemical reaction equation for the flexible urea-formaldehyde resin prepolymer is:

[0026]

[0027] The curing agent obtained after curing flexible urea-formaldehyde resin microcapsules grafted with epoxy functional groups (KH560) is as follows:

[0028]

[0029] The beneficial technical effects obtained by this invention are as follows:

[0030] 1. Using the technical solution of this invention, urea, formaldehyde, and flexible modified monomer n-butylamine are used to generate a flexible urea-formaldehyde resin prepolymer under the action of an alkaline catalyst. The flexible urea-formaldehyde resin prepolymer is mixed and emulsified with an anhydride curing agent and an accelerator to prepare an anhydride curing agent with flexible microcapsules. Due to the presence of flexible carbon chains, the capsule wall material of the curing agent can effectively improve the cracking problem caused by the large shrinkage of microcapsule curing, improve the uniformity and density of the capsule wall, and is not easy to break during transportation, high-speed stirring and coating.

[0031] 2. By adopting the technical solution of the present invention, the introduction of flexible carbon chains into urea-formaldehyde resin can also prevent problems such as premature gelation caused by microcapsule rupture during transportation or high-speed stirring, as well as bubble perforation during coating. It can be stirred quickly without worrying about microcapsule rupture, saving raw materials, time and labor costs.

[0032] 3. By adopting the technical solution of the present invention, the surface of the flexible microcapsule is modified and epoxy functional groups are grafted onto the surface of the flexible microcapsule, so that the microcapsule is more uniformly dispersed in epoxy resin, less prone to sedimentation, and has excellent curing efficiency and uniformity.

[0033] 4. Using the technical solution of the present invention, flexible urea-formaldehyde resin microcapsules with surface-grafted epoxy functional groups are dispersed in an aqueous epoxy film. Under high temperature, the capsule wall material is easily broken. After the curing agent and accelerator are released, they react with the epoxy groups in the epoxy resin to achieve curing and crosslinking. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are some embodiments of this application, but not all embodiments.

[0035] This invention provides a flexible modified microcapsule-coated anhydride curing agent. By introducing linear alkylamines as flexible materials into an epoxy resin system, a flexible urea-formaldehyde resin prepolymer is generated, which is then used to prepare a flexible microcapsule-coated anhydride curing agent. Due to the presence of flexible carbon chains, the capsule wall material of the curing agent can effectively improve the cracking problem caused by the large shrinkage of microcapsule curing, improve the uniformity and density of the capsule wall, and is not easily broken during transportation, high-speed stirring, and coating.

[0036] Meanwhile, grafting epoxy functional groups with -Si-O- structures onto the outer side of the capsule wall enables the microcapsules to be more uniformly dispersed in the epoxy resin, making them less prone to sedimentation, and also improves the uniformity of the curing agent.

[0037] The technical solution of the present invention will be described in detail below through specific embodiments.

[0038] Example 1

[0039] The preparation method of the flexible modified microcapsule-coated anhydride curing agent provided in this embodiment includes the following steps:

[0040] 1. Preparation of flexible urea-formaldehyde resin prepolymer:

[0041] Six parts by mass of formaldehyde were prepared into a 30% formaldehyde aqueous solution and poured into a three-necked flask equipped with a stirrer and a temperature measuring device. The temperature was heated to 40°C, and 10 parts by mass of urea and 1 part by mass of the flexible modifier n-butylamine were slowly added while stirring. The slow addition of urea can reduce free formaldehyde. After the urea was completely dissolved, the pH of the solution was adjusted to 9 using triethanolamine, the temperature was raised to 80°C, and the reaction was carried out at 2000 R / min for 1 hour to prepare a transparent and viscous flexible urea-formaldehyde resin prepolymer. After cooling to room temperature, the pH was adjusted to 7 with dilute hydrochloric acid for later use.

[0042] 2. Emulsion preparation:

[0043] A 5% aqueous solution of emulsifier, wherein the emulsifier is sodium dodecyl sulfate, is added to a three-necked flask equipped with a stirrer and a temperature measuring device. Resorcinol and methyltetrahydrophthalic anhydride are added to the aqueous solution as curing agent and accelerator, respectively. The mixture is stirred at 1200 R / min for 0.5 h to form a stable oil-in-water (O / W) emulsion.

[0044] 3. Synthesis of flexible microcapsules:

[0045] The prepared flexible urea-formaldehyde resin prepolymer was added to the emulsion prepared in step 2. The mass ratio of prepolymer to emulsion was 20:100. The pH was adjusted to 3 with dilute hydrochloric acid, and 0.1 parts of defoamer isooctyl alcohol were added. The water bath was slowly heated to 55°C and maintained at 500 R / min for 2 hours. After complete curing, the emulsion-like flexible microcapsule curing agent was obtained.

[0046] 4. Surface treatment of flexible microcapsules

[0047] Three parts by weight of KH560 were added to the emulsion-like flexible microcapsule curing agent in step 3, and the reaction was carried out at 55°C and 1000 R / min for 1 hour. The product was cooled to room temperature, filtered, and washed with water until neutral to obtain a flexible urea-formaldehyde resin microcapsule curing agent with epoxy functional groups grafted on the surface.

[0048] Example 2

[0049] The difference between this embodiment and Example 1 is that the amount of flexible modifier n-butylamine added is 0.8 parts by weight.

[0050] Example 3

[0051] The difference between this embodiment and Embodiment 1 is that the amount of flexible modifier n-butylamine added is 1.5 parts by weight.

[0052] Compare with Example 1

[0053] The difference between this comparative example and Example 1 is that the flexible modifier n-butylamine is not added in step 1.

[0054] Compare with Example 2

[0055] The difference between this comparative example and Example 1 is that the microcapsules are not surface modified, that is, step 4 is not performed.

[0056] Compare with Example 3

[0057] The difference between this comparative example and Example 1 is that n-propylamine was added as a flexible modifier in step 1.

[0058] Compare with Example 4

[0059] The difference between this comparative example and Example 1 is that the amount of flexible modifier n-butylamine added is 2 parts by mass.

[0060] Compare with Example 5

[0061] The difference between this comparative example and Example 1 is that n-heptylamine was added as a flexible modifier in step 1. During the operation, the system viscosity was too high during the preparation of the prepolymer, making it impossible to prepare the urea-formaldehyde resin prepolymer. No performance testing was performed in this comparative example.

[0062] The microcapsules prepared in the above examples and comparative examples were added to the aqueous epoxy resin and mixed at a mass ratio of 1:15 to form a mixed system with a solid content of 40 wt%.

[0063] The above mixture is evenly coated onto PE release paper and baked at 50-60°C for 10-30 minutes. After it is completely dry, a double-sided polyurethane film product with a thickness of 50μm is obtained.

[0064] Before use, peel off the PE release paper on the surface of the polyurethane film product and attach both sides of the polyurethane film product to the object to be bonded, such as ink glass or substrate. The latent curing agent is released by breaking the capsule wall of the microcapsule through hot pressing, and then rapidly crosslinks with the hydroxyl active groups in the water-based polyurethane. The reaction is completed in 60 seconds.

[0065] The specific conditions for hot pressing are 70–100℃ and an application rate of 1–2 kg / cm². 2 The pressure.

[0066] The adhesive properties of the polyurethane films prepared in the examples and control examples were tested after storage for 5 days, 15 days and 30 days, respectively.

[0067] The testing method includes: removing the PE release paper from the surface of the polyurethane film product; adhering one side to an ink-coated glass substrate as a base layer; and applying a primer substrate (aluminum alloy or stainless steel) to the other side; and testing at 50℃ and 1.5 kg / cm². 2 Pre-compression for 10 seconds under pressure, then apply pressure of 1.5 kg / cm². 2 Under the conditions of pressing at 90℃ for 60 seconds, the 90° peel force was tested using an electronic tensile testing machine (Instron 3400). The test results are shown in Table 1.

[0068] Table 1. Peel force test results for the examples and control examples.

[0069]

[0070] As can be seen from the above test results, the microcapsules obtained by using the technical solutions provided in Examples 1-3 of this invention can still maintain stable adhesive properties after 30 days of storage, while the adhesive properties of Control Example 1, without the addition of a flexible modifier, decreased significantly after 30 days of storage.

[0071] The above are merely preferred embodiments of the present invention and do not limit the scope of protection of the present invention. For those skilled in the art, the present invention can have various modifications and variations. Any changes, modifications, substitutions, integrations, and parameter alterations to these embodiments within the spirit and principles of the present invention, achieved through conventional substitutions or by achieving the same function without departing from the principles and spirit of the present invention, fall within the scope of protection of the present invention.

Claims

1. A method for preparing a flexible modified microcapsule-coated anhydride curing agent, characterized in that, Includes the following steps: S1. Preparation of flexible urea-formaldehyde resin prepolymer: A flexible urea-formaldehyde resin prepolymer is prepared by mixing formaldehyde, urea and flexible modified monomers; S2. Preparation of emulsion: Emulsifier, resorcinol, curing agent and accelerator are added to an aqueous emulsifier solution to form a stable oil-in-water (O / W) type emulsion; S3. Preparation of curing agent The flexible urea-formaldehyde resin prepolymer prepared in S1 and the emulsion prepared in S2 are mixed and then cured to obtain an emulsion-like flexible microcapsule curing agent. S4. Surface Treatment A surface modifier is added to the flexible microcapsule curing agent prepared by S3 for reaction, and the surface modifier is grafted onto the flexible microcapsule curing agent for surface treatment to obtain a flexible urea-formaldehyde resin microcapsule curing agent with epoxy functional groups grafted on the surface. In S1, the flexible modified monomer is n-butylamine; The mass ratio of the flexible modified monomer to formaldehyde is 1:4~8.

2. The preparation method of the flexible modified microcapsule-coated anhydride curing agent according to claim 1, characterized in that, The curing agent is an acid anhydride curing agent; the accelerator is 2-ethyl-4-methylimidazole.

3. The preparation method of the flexible modified microcapsule-coated anhydride curing agent according to claim 1, characterized in that, The surface modifier is an alkoxy compound containing -Si-O- bonds.

4. The preparation method of the flexible modified microcapsule-coated anhydride curing agent according to claim 3, characterized in that, The surface modifier is KH560.

5. The method for preparing the flexible modified microcapsule-coated anhydride curing agent according to any one of claims 1-4, characterized in that, The mass ratio of the surface modifier to formaldehyde is 0.02~0.1:

1.

6. A flexible modified microcapsule-coated anhydride curing agent, prepared by the preparation method described in any one of claims 1-5.

7. A heat-activated epoxy film, prepared by the flexible modified microcapsule-coated anhydride curing agent prepared by the preparation method of the flexible modified microcapsule-coated anhydride curing agent as described in any one of claims 1-5, or by the flexible modified microcapsule-coated anhydride curing agent as described in claim 6.

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